class_docstr: Abstract base class for Atari wrappers.
  
  This assumes that the input environment is a dm_env.Environment instance in
  which observations are tuples whose first element is an RGB observation and
  the second element is the lives count.
  
  The wrapper itself performs the following modifications:
  
    1. Soft-termination (setting discount to zero) on loss of life.
    2. Action repeats.
    3. Frame pooling for action repeats.
    4. Conversion to grayscale and downscaling.
    5. Reward clipping.
    6. Observation stacking.
  
  The details of grayscale conversion, downscaling, and frame pooling are
  delegated to the concrete subclasses.
  
  This wrapper will raise an error if the underlying Atari environment does not:
  
  - Exposes RGB observations in interleaved format (shape `(H, W, C)`).
  - Expose zero-indexed actions.
  
  Note that this class does not expose a configurable rescale method (defaults
  to bilinear internally).
  
  This class also exposes an additional option `to_float` that doesn't feature
  in other wrappers, which rescales pixel values to floats in the range [0, 1].
docstr: Returns the raw observation, after any pooling has been applied.
docstr_tok: ["Returns","the","raw","observation",",","after","any","pooling","has","been","applied","."]
code: def raw_observation(self) -> np.ndarray:
      """Returns the raw observation, after any pooling has been applied."""
      assert self._raw_observation is not None
      return self._raw_observation
  
imports: import abc
  from typing import Tuple, List, Optional, Sequence, Union
  from acme.wrappers import base
  from acme.wrappers import frame_stacking
  import dm_env
  from dm_env import specs
  import numpy
  from PIL import Image
label_desc: Use image node_id 11 for calling the BaseAtariWrapper obj's underlying member method code with example usage: obj.raw_observation() and returns: self